Pressure of Urbanisation on the Fish Community Structure in Küçük Menderes River Basin (Turkey)

Urbanization is linked to changes in aquatic flora and fauna, including fishes, and it often leads to a decline in fish diversity, richness, and density. This study aims to determine the fish fauna and their abundance in Küçük Menderes River Basin, which is under the threat of urbanization. The field surveys were carried out in 50 different locations in lotic and lentic biotopes, and fish sampling was performed by using electro-shocker, seine-net, and gillnets in November 2017 and May 2018. A total of 21 taxa belonging to 14 families (Anguillidae, Acheilognathidae, Atherinidae, Blenniidae, Cobitidae, Cyprinidae, Gobiidae, Leuciscidae, Mugilidae, Nemacheilidae, Percidae, Poecilidae, Siluridae and Syngnathidae) was identified. Cyprinidae has the highest species richness with four taxa and the most commonly found fish species were Squalius kosswigi and Cyprinus carpio. In terms of abundance of species, Gambusia holbrooki was the most dominant fish species in Hırsız (the catch per unit effort = 23.28 n/min/m2) and Kuskudan (the catch per unit effort = 24.00 n/min/m2) streams. While Alburnus demiri, Barbus pergamonensis, Cobitis fahireae, Oxynoemacheilus germencicus, Petroleuciscus smyrnaeus and S. kosswigi are Anatolian endemics, Atherina boyeri, Carassius auratus, C. gibelio and Gambusia holbrooki are the invasive fish species in the basin.